A colonoscopy is a procedure where a physician uses a flexible, thin tube with a camera and light source to examine the inside of the rectum and colon.
A colonoscopy can detect inflamed tissue, ulcers, and abnormal growths such as polyps and tumors. The procedure is now the gold standard and commonly used to detect or prevent individuals from getting colon cancer. Adults starting at age 45 years are strongly recommended to have a colonoscopy or some other test to screen for colon cancer. Individuals with a family history of colon cancer or other conditions such as inflammatory bowel disease are often advised to have a colonoscopy for cancer screening at an earlier age. It is also used to evaluate people with unexplained changes in bowel habits, diarrhea, constipation, abdominal pain, bleeding from the anus or rectum, and weight loss.
The colon and rectum needs to be cleared of any stool residue before the colonoscopy is performed. Written instructions on how to prepare for the colonoscopy will be given to all patients. Patients will be required to restrict their diet starting 3 days before the procedure. Patients will usually start to drink a strong laxative several hours before the procedure time.
It is very important for patients to follow the instructions for the colonoscopy preparation as closely as possible and for patients to complete the laxative preparation as instructed by their physician. Failure to follow these instructions can lead to too much stool residue in the colon, which impairs the physician to detect polyps and tumors and thus limit the procedure’s effectiveness in reducing patients’ risk of colon cancer. A colon that is not properly cleansed of stool residue will often require the physician to abort the colonoscopy and require the patient to repeat the diet and laxative preparation and colonoscopy on a different day.
Generally, no eating or drinking is allowed for 4 to 8 hours before the procedure. Smoking and chewing gum are also prohibited during this time. Patients should tell their doctor about all health conditions they have—especially heart and lung problems, diabetes, and allergies— and all medications they are taking. Medications and vitamins that may be restricted before and after upper GI endoscopy include:
Driving is not permitted for 24 hours after the procedure to allow sedatives time to completely wear off. Before the appointment, patients should make plans for a ride home.
Colonoscopies are performed at a hospital or outpatient center. Patients will first change into a gown and their belongings will be stored in a secure area. An intravenous (IV) needle is placed in a vein in the arm so sedatives can be administered. Sedatives help patients stay relaxed and comfortable. Most patients fall asleep with sedatives during the procedure. While patients are sedated, the doctor and medical staff monitor vital signs. Patients continue to breathe on their own throughout the procedure.
During colonoscopy, patients lie on their left side on an examination table. The doctor inserts a long, flexible, lighted tube called a colonoscope, or scope, into the anus and slowly guides it through the rectum and into the colon. The scope inflates the large intestine with air to give the doctor a better view. A small camera mounted on the scope transmits a video image from inside the large intestine to a computer screen, allowing the doctor to carefully examine the intestinal lining. The doctor may ask the patient to move periodically so the scope can be adjusted for better viewing. Once the scope has reached the opening to the small intestine, it is slowly withdrawn and the lining of the large intestine is carefully examined again.
A doctor can remove growths, called polyps, during a colonoscopy and later test them in a laboratory for signs of cancer. Polyps are common in adults and are usually harmless. However, most colorectal cancer begins as a polyp, so removing polyps early is an effective way to prevent cancer. The doctor can also take samples from abnormal-looking tissues during colonoscopy. The procedure, called a biopsy, allows the doctor to later look at the tissue with a microscope for signs of disease.
After the colonoscopy, patients are moved to a recovery room where they wait about an hour for the sedative to wear off. During this time, patients may feel abdominal pain, bloating or nausea. Patients will likely feel tired and should plan to rest for the remainder of the day. Unless otherwise directed, patients may immediately resume their normal diet and medications.
Some results from the colonoscopy are available immediately after the procedure. The doctor will often share results with the patient after the sedative has worn off. Biopsy results are usually ready in one to two weeks.
Overall, the risks associated with colonoscopy are low. Bleeding can occur from a biopsy or removal of a polyp or growth from the colonoscopy, but such bleeding often stops on its own or can be controlled through the colonoscopy. Perforation (a hole or a deep tear in the lining of the colon or rectum) may require surgery, but this is an uncommon complication. Injury to other organs such as the spleen can occur, but is very rare. Other risks involve complications related to the anesthetics and sedatives, (breathing difficulties, aspiration) or complications related to heart and lung disease.
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